Intracranial Aneurysm Enlargement on Serial Magnetic Resonance Angiography

BACKGROUND AND PURPOSE: Size of an unruptured intracranial aneurysm (UIA) may be an important risk factor for rupture. Accordingly, serial noninvasive imaging is commonly used to assess untreated UIA for enlargement. Few data exist regarding the frequency and predictors of enlargement. We obtained this information from a group of patients followed with serial MR angiography (MRA). METHODS: We retrospectively identified 165 patients with 191 UIA followed with serial MRA. Fusiform aneurysms, UIA or=13 mm, respectively (Por=8 mm in diameter were at highest risk for enlargement (OR, 7.25; 95% CI, 1.96 to 27.1). There was a trend toward increased risk of enlargement in patients with multiple aneurysms (OR, 2.50; 95% CI, 0.86 to 7.53). CONCLUSIONS: Over a median follow-up period of 47 months, 10% of UIA enlarged. Larger aneurysms had a significantly increased risk of enlargement. The likelihood of enlargement was highest in aneurysms with diameters >or=8 mm. However, a clinically significant proportion of small aneurysms grow, and this growth can be detected by serial MRA.